Conventionally, miniature unmanned aerial vehicles (UAVs) which are typified by unmanned helicopters for industrial use have been expensive and hard to obtain and manipulative skills have been needed to make them fly stably. Recently, however, UAV maneuverability has improved dramatically because an acceleration sensor, an angular velocity sensor, etc. which have high performance and are easy to handle have become available at reasonable prices, and also, many operations to control the UAV airframe have been automated. Against this background, attempts are now made to apply, especially, miniature multicopters to diverse missions in a wide range of fields, not only for hobby purposes.
A multicopter is one type of a helicopter having a plurality or rotors installed thereon, and it flies while keeping balance by adjusting the rotational rate of each of these rotors. Unlike a helicopter, a multicopter has a simplified structure, and therefore, the multicopter is easy to maintain and its airframe can be built at comparatively low cost.